Copper alloy and process of treating same



Patented Feb. 10,1931

" "UNITED ISTATVESQ'PATENTQ 01:15a

MICHAEL G; CORSON, or .mcxsoir HEIGHTS,\NEW YORK, ASSIGNOR or animu-'rwEN rIETHs 'ro GEORGE E. COREY, or 'IBAYSIDE, 'Nnw Yum:

corrEnALLoY AND riioozessor TREATING sum 2N0 Drawing.

This invention relates to a process of treating alloys to impartdesirable properties thereto and the product-produced thereby. Inparticular, the invention relates to a class 5 of alloysconsistingprincipally of copper,

tin and zinc, and characte'rized,when treated according to the processhereinafter disclosed, by properties giving them special utility whenused in forming lubricated Wearing surfaces, such, for example, as inbearings,

bushings, pump cylinders, gears, etc.-

' The most important feature ofthe coppertin alloys (tin bronzes) thatcauses them to be especially suitable for use in bearings and in similarsituations where resistance to wear is desirable, is their peculiarstructure inthe cast state, which is characterized by the presence of asoft ground mass serving as amatrix for, and containing inclusions of, asec- 0nd constituent,-the delta phase,of considerable hardness, soforming a very desir able complex possessing goodlbearing qualities.

Other alloys used for bearings,'or more specifically for bushings,

zinc brasses composed of a high proportion of copper in alpha phase anda low proportion in beta or delta phase. These alloys, while they arecheaper than the high tin bronzes and can be hot worked ,with ease,since at high temperatures they transform into a uniform beta phase, areless satis actory for bearing purposes than the tin bronzes, eitherbecause of insufficient hardness (too great a 5 proportion of the softeralpha phase as com-- pared with the harder beta phase) or because of thedistribution of the harder phase in the softer ground mass in such a wayas to present an excessive amount thereof at the wearing surface withconsequent lack of ability to retain an adequate oil film thereon.

While alpha copper' alloys are workable cold and to a slight extent whenhot and the beta alloys are all workable hot,'such alloys as are betaphases, at any temperature below the freezing point, are noteasilyworkable by pressure or tension either in the hot or cold state. Hightin bronzes are not exempt from the are certain high built up ofmixtures of the alpha and Application filed February 1e, 1929. Serialno} 340,651.

The bronzes containing between 6 and 18% tin cannot be worked :wli'ilehot. Such alloys containing above 18%, and up t r27%, tin are easilyworkable while hot, but are relatively expensive, and,

action of this rule.

what is more important, are at room temperatures too brittle. and hardthroughout their structure to be useful as structural materials or forbearings and bushings' v I havefound that ternary bronzes can be 'inadeto behave much like complex brasses (alpha plus beta) in their abilityto be hot to retain a high, strength with-considerable ductility iii thecold state. Also, they possess the property of high tin bronzes of beingable toform a well distributed delta tin constituent of high hardness,which makes them good for wear resistance, not only because of V theinherent hardness of such constituent, but also because theuniformdistribution of the delta constituent in suitably sized particlesthroughout the ground mass or matrix im-' parts to a wearing surfaceprepared therefrom the abilityuto become covered with a substantial filmof lubricant, in the regions .occupied by the softer alpha constituentof the matrix. y

,I have also found that such ternary bronzes can be markedly improved bystructural changes resultingfrom a process of heat treatment.

. Alloys coming within the present invention can be prepared within thefollowing range The amounts of zinc and tin depend each upon the other.The more zinc the alloy conworked when brought into the beta state andtains, the less tin it may contain. Small" Q amounts of nickel up-to10%, and preferably around to 3%, may be substituted for an equal amountoficopper, and either a part-of the tin or the zinc may be, replaced byabout half its weight of aluminum, aluminum preferably, however, notbeing added in amounts greatly exceeding 1% of the total. Iron andcobalt in amounts of from-0.3 to2.0% may also form useful but notabsolutely necessary additions. These alloys may. also contain smallamounts of magnesiumfphosphorus, silicon or manganese-used asdeoxidizers. When aluminum is present-amounts of manganese up to-4% maybe added with very benelieial results. l

These alloys can be used as cast or be hot 7 worked by forging,rollingfor especially, by m extrusion; but-to improve their structuralfeatures and ensuing properties it is nec-' essary to subject them toheat treatment, as follows:

Y. The cast or hot workedpiece is-heated up 15 to orabove a point wherethe alloy forms a homogeneous beta phase or a mixture of the .two betaspossible,,650-800 Cl, according to the composition,-and then quenched orair cooled. This brings it into a hard mar 'gn tensitoidal or acicul'arform. It is next heat ed to a point above the eutectoidal point, or from550625 C., and kept at this temperal ture for from one to six hours,*oruntil the acicular structure is destroyed and the beta 2.. phasedivorces from the.'alpha; the first ,coa=

lescing in the form of ,well-rounded dense grainlets 'sufliciently wellspaced within the .matrix of alpha to permit the formation of alubricating film on the surface when in use.

perature preferably to 450525 C., and not below 250 C., and holding suchtemperature (fior such time as to' allow thejbeta phase to i'ssociateinto alpha-plus delta, the latter 55 forming very fineparticles withineach original-grainlet of beta, When this condition is reached thestructure will have become stabilized. g

WhatI claim is 1. Process of treating alloys containing 4.-18% tin and35% zinc, with the balance principally, copper, to improve theirproperties for use as lubricated wearingrsurfaces, comprising heatingthe alloyto The next step consists in lowering the tem om 650? to 800(1., and qulckly cooling toproduce a "hard acicular structure, thenreheating to alloy to produce a structure characterizedby the presenceof beta crystals uniformly distributed throughout 'a matrix. of alphacrystals, followed by slow cooling to produce bilized.

zinc, withthe balance'principally copper, and kchar'acterized' by a.physical structure and d into alpha 1'75 then reso. plusdelta and ,thestructure has become stav M article of. manufacture consisting. of analloy containing 4.918% tin and 10-35% properties such as areproducedwhen an alloy of like composition is heated to from 050. to 800 quicklycooled, then reheated yto from 550 to 625 C; and held at suchtemperature for sufficient-time to destroy the acicul'ar structure"? andproduce .a stru ture characterized by the presence of a beta aseconstituent uniformly distributed through out; a matrix of an alphaphaseconstituent,

and finally gradually cooled at such a rate as to'promote dissociationof the beta form into alpha plus delta. l In testimony whereof, I havesigned my. name to' this specification this 11th Feb. ,1929.

MIQHAEL G. coasoN;

day or 1 10 lee.

from 550 to 625 0., maintaining the alloy at such temperature forsuflicient time; to destroy the acicularstructure-and produce 50 astructure characterized by the presenceof 4 beta'crystals uniformlydistributed throu' h out a matrix of alpha crystals, and finally.

, gradually pooling the alloy at-s'uch a rate as to promote dissociationof the alpha plus delta.

2. Process of ties as lubricated wearing surfaces, compr1sbeta form intotreating alloys containing 4-18% tin and 10-35% zinc, yviththe balanceprincipally copper, to improve their proper-.

ing heating the alloy for such time and at such temperature as to bringabout a uniform beta stateof the alloy constituents, then quicklycooling to produce a hard aeicular;

structure, then reheating to .a point above the eutectoidaltransformation point forthe t CERTIFICATE or connncrrou;

LP a tent No;"1,7 92, l46.' i GrantedfFehru arj lm i931,to I

t. MICHAEL q. CORSDN.

* It is hereby certified that error appears inthe printed specificationfof the above numbered patent requiring correction as follows: .Page -l,strike out the table between lines 85to 89, and in sertinstead ,Tin41s%- Zinc '10 35% v Copper balance;

and that the said Letters Patent should be read with this correctiontherein that 7 Q the same may conform to the record of the case in thePatent'office.

. Signed and sealed this 17th day of March, '1931.

v '(Senl) I Acting Commissioner of Pntentg.

